Our goal is to study the expression and function of the Qa and TL cell surface antigens determined by the major histocompatibility complex of the mouse. The Qa and TL molecules have several unique characteristics which suggest that they may have an important role in immune functioning and/or leukemogenesis. We will use molecular cloning techniques to study their polymorphism, regulation, structure, antigenicity, differentiation, and function. Techniques to be used include molecular cloning, restriction enzyme mapping, DNA-mediated gene transfer, exon shuffling, cytotoxicity tests, radioimmune assays, functional analysis of T cell killing, and the induction of leukemias.